The present invention relates to a method for the indirect oxidation of urea by means of an electrochemical cell, having two electrodes, to which an aqueous chloride-containing urea solution is supplied, as well as apparatus for the practice of this method.
Hemodialysis and hemofiltration as well as peritoneal dialysis are methods for the removal of urea from the blood of kidney patients. These treatment methods have become firmly established in the clinical sector and have become routine therapeutic procedures. However, the capacity of the existing dialysis centers is not sufficient for the necessary treatments of the kidney patients. A solution to this situation is home dialysis, which can be carried out by the patient himself. For home dialysis, however it is imperative to reduce the dialysis and substitution solutions required for the patient. Heretofore, in fact, one has discarded the urea-containing electrolyte obtained in extra-corporal plasma regeneration, i.e., in blood purification, the blood filtrate, and a substitution solution had to be available. At present, between 100 and 300 liters of dialysis solution are required per treatment for hemodialysis and about 20 liters of replacement solution for hemofiltration.
Attempts have been undertaken to purify the urea-containing dialysate electrochemically by indirect oxidation of urea. To this end, the dialysate is fed into an electrochemical cell which contains two parallel electrodes in a chamber (cf. "Medical & Biological Engineering and Computing", vol. 16, 1978, pages 25 to 30). An important step here is the formation of hypochlorite, which is formed from the (sodium) chloride present in the dialysate. The following reactions proceed at the electrodes:
Anode: 6Cl.sup.- .fwdarw.3Cl.sub.2 +6e.sup.- ; PA0 Cathode: 6Na.sup.+ +6H.sub.2 O+6e.sup.- .fwdarw.6NaOH+3H.sub.2.
Provided the anodic and cathodic reaction products, i.e., chlorine and sodium hydroxide, ae thoroughly mixed, hypochlorite then forms: EQU 6NaOH+3Cl.sub.2 .fwdarw.3NaOCl+3NaCl+3H.sub.2 O.
The formed hypochlorite is a strong oxidizing agent, which reacts with the urea in the following manner: EQU (NH.sub.2).sub.2 CO+3NaOCl.fwdarw.N.sub.2 +CO.sub.2 +2H.sub.2 O+3NaCl.
Under favorable conditions, therefore, the urea should be completely transformed into nitrogen, carbon dioxide, and water. In practice, however, it has been found that the conversion is not complete. In addition, a pH shift occurs, and chlorine and hypochlorite remain in the treated liquid, so that a reinfusion with this liquid cannot be performed.